Modified Polyethylene Terephthalate Surfaces Research Articles

Atmospheric Plasma and UV Polymerisation for Developing Sustainable Anti-Adhesive Polyethylene Terephthalate (PET) Surfaces

Enhancing the hydrophilicity of polymeric materials is an important step for achieving anti-adhesiveness. Thus, in this study, atmospheric plasma as a pre-treatment was combined with a UV grafting process to obtain a durable surface modification on polyethylene terephthalate (PET). The most promising conditions for the atmospheric plasma process were found to be 15 kW power and 4 m/min speed, leading to a contact angle reduction from 70 ± 6° to approximately 30°. However, it was observed that these values increased over time due to the ageing and washing of the PET surface, ultimately causing it to recover its initial contact angle. Therefore, the plasma-pre-treated PET samples were further modified through a UV grafting process using sodium acrylate (NaAc) and 3-sulfopropyl acrylate potassium salts (KAc). The grafted acrylate PET samples exhibited contact angles of 8 ± 3° and 28 ± 13° for NaAc and KAc, respectively, while showing durability in ageing and washing tests. The dry film thicknesses for both samples were found to be 28 ± 2 μm. Finally, the anti-adhesive properties of the NaAc- and KAc-treated surfaces were evaluated using an Escherichia coli expressing YadA, an adhesive protein from Yersinia. The modified PET surfaces were highly effective in reducing bacterial adhesion by more than 90%.

Can Superhydrophobic PET Surfaces Prevent Bacterial Adhesion?

Prevention of bacterial adhesion is a way to reduce and/or avoid biofilm formation, thus restraining its associated infections. The development of repellent anti-adhesive surfaces, such as superhydrophobic surfaces, can be a strategy to avoid bacterial adhesion. In this study, a polyethylene terephthalate (PET) film was modified by in situ growth of silica nanoparticles (NPs) to create a rough surface. The surface was further modified with fluorinated carbon chains to increase its hydrophobicity. The modified PET surfaces presented a pronounced superhydrophobic character, showing a water contact angle of 156° and a roughness of 104 nm (a considerable increase comparing with the 69° and 4.8 nm obtained for the untreated PET). Scanning Electron Microscopy was used to evaluate the modified surfaces morphology, further confirming its successful modification with nanoparticles. Additionally, a bacterial adhesion assay using an Escherichia coli expressing YadA, an adhesive protein from Yersinia so-called Yersinia adhesin A, was used to assess the anti-adhesive potential of the modified PET. Contrarily to what was expected, adhesion of E. coli YadA was found to increase on the modified PET surfaces, exhibiting a clear preference for the crevices. This study highlights the role of material micro topography as an important attribute when considering bacterial adhesion.

Introduction and optimization of the in-vitro method for determining the hemocompatibility of modified poly(ethylene)terephthalate surfaces

Purpose: Internationally-accepted standards have been developed for a range of tests and parameters for characterising the in-vitro interactions of biomaterials with blood. However, there are, as yet, no standards concerning the size, design and type of such in-vitro testing systems (1). Since the development of hemocompatible biomaterials provides a very important challenge in material science, there is a need for further progress in finding reliable and standardized methods for hemocompatibility testing (2). The aim of this research was to introduce a method for analyzing the hemocompatibility of different chemically-modified surfaces. Polyethylene terephthalate (PET), with surface modifications using differentpolysaccharides and their derivatives, were chosen because of their promising biocompatible properties and numerous potential biomedical applications.Methods: A modified hemoglobin-free method was used to determine the antithrombogenicity of the modified PET surfaces (4). The method was optimized for shaking rate, the addition of buffer, and blood temperature to decrease measuring errors. Five differently-modified PET surfaces were analyzed: chemically pre-treated PET and PET treated with chitosan, fucoidan, sulphated chitosan and heparin. Glass was used as a standard thrombogenic surface.Results: The results showed that a lower shaking rate, the addition of buffer, and blood cooling prior to measurement significantly decreased the standard deviation of the measurement results by a total of about 89 %.Conclusions: We believe this optimized hemoglobinfree method is suitable for distinguishing between chemically and structurally-different surfaces, such as glass and PET. The differences between PET surfaces coated with different polysaccharides were, however, less pronounced.

Modulation of neo-endothelialization of vascular graft materials by silk fibroin.

Controlled neo-endothelialization is critical to the patency of vascular grafts. Expanded polyethylene terephthalate (PET) vascular grafts were grafted with polyethylene glycol (PEG), irradiated with ultraviolet light, and subsequently coated with silk fibroin (SF) and EDC in a dip-coating process. Endothelial cells were cultivated on the coated samples for 1, 3, 5, and 7days, and characterized by fluorescence microscopy and scanning electron microscopy (SEM). The quantitative analyse of CCK-8 method was used to assess ECs proliferation. The results reveal the correlation between grafting components and cell adhesion. We demonstrated that PET with SF grafting facilitated cell adhesion and spreading. Following 7days of cell culture in vitro, PET-PEG6000-SF (PEG molecular weight 6,000) displayed spreading of cells over a significantly larger area. Rapid endothelialization on a modified PET surface resulted in large tissue pack that can be observed by SEM.

Kinetic study of NTPDase immobilization and its effect of haemocompatibility on polyethylene terephthalate

Poor haemocompatibility of material surfaces is a serious limitation that can lead to failure of blood-contacting devices and implants. In this work, we have improved the haemocompatibility of polyethylene terephthalate (PET) surfaces by immobilizing apyrase/ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) on to the carboxylated PET. NTPDase immobilized PET surfaces scavenge the ADP released by activated platelets, which prevents further platelet activation and aggregation. The surface properties of the modified PET were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDAX), and contact angle measurement. The enzyme attachment and stability on the modified PET surfaces were evaluated. The kinetics of free enzyme and immobilized enzyme were studied and fitted using the Michaelis-Menten kinetic model. Both free and immobilized NTPDase followed Michaelis-Menten kinetics with similar Michaelis-Menten constants (Km). This suggests that the activity of NTPDase was unchanged upon immobilization. Protein adsorption and %hemolysis was significantly reduced for carboxylated PET and NTPDase immobilized PET surfaces compared to unmodified PET. Lactate dehydrogenase assay showed that the number of adhered platelets reduced by more than an order of magnitude for the NTPDase immobilized PET surface compared to unmodified PET. These results clearly indicate that NTPDase immobilization significantly enhances the haemocompatibility of PET surfaces.

Surface characterization and free thyroid hormones response of chemically modified poly(ethylene terephthalate) blood collection tubes

The surface chemistry and surface energy of chemically modified polyethylene terephthalate (PET) blood collection tubes (BCTs) were studied and the results showed a significant increase in hydrophilicity and polarity of modified PET surface. The surface modification created nanometer-sized, needle-like asperities through molecular segregation at the surface. The surface dynamics of the modified PET was examined by tracking its surface properties over a 280-day period. The results showed surface rearrangement toward a surface with lower surface energy and fewer nanometer-sized asperities. Thromboelastography (TEG) was used to evaluate and compare the thrombogenicity of the inner walls of various types of BCTs. The TEG tracings and data from various types of BCTs demonstrated differences in the reactionand coagulation times but not in clot strength. The performance of the modified tubes in free triiodothyronine (FT3) and free thyroxine (FT4) hormone tests was examined, and it was found that the interference of modified PET tubes was negligible compared to that of commercially available PET BCTs.

Spectroscopic Diagnostics of Enhanced Magnetron and Mesh Separation Effects in Cyclonic Atmospheric Pressure Plasma Surface Modification of Polyethylene Terephthalate

The correlation of plasma surface modification consequence and the electron characteristics in plasma state with the enhanced magnetron source and metal mesh screen are studied by cyclonic-atmospheric-pressure plasma on polyethylene terephthalate (PET) surface. The contact angle measurement is employed to examine the plasma modified PET surface hydrophilicity. Optical emission spectroscopy is used to detect the electronic excitation temperature and electron density in cyclonic atmospheric pressure plasma. The electronic excitation temperature and the electron density are measured as the operational conditions of adding magnetron source and metal mesh separation. Boltzmann plot method is employed to estimate the electronic excitation temperature whereas electron density measurement by the Voigt profile. The results show that both electronic excitation temperature and electron density have similar trend i.e., both increasing with the enhanced magnetron source while decreasing trend is observed with passing through the metal mesh.

Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV–vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

“Short” Dithiol and Au Nanoparticles Grafting on Plasma Treated Polyethyleneterephthalate

Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiol (4,4-bifenyldithiol, BFD)) to create thiol (-SH) groups on polymer surface. This short dithiol is expected to be fixed via one of-SH groups to radicals created by the plasma treatment on the PET surface. Free-SH groups are allowed to interact with Au nanoparticles. Xray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Electrokinetic Analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the samples were studied by Atomic Force Microscopy (AFM).The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on modified surface in the case of bifenyldithiol pretreatment. The rigid molecule of biphenyldithiol is bounded via only one-SH group to the modified PET surface and the second one remains free for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface.

Influence of argon plasma on the deposition of Al2O3 film onto the PET surfaces by atomic layer deposition

In this paper, polyethyleneterephthalate (PET) films with and without plasma pretreatment were modified by atomic layer deposition (ALD) and plasma-assisted atomic layer deposition (PA-ALD). It demonstrates that the Al2O3 films are successfully deposited onto the surface of PET films. The cracks formed on the deposited Al2O3 films in the ALD, plasma pretreated ALD, and PA-ALD were attributed to the energetic ion bombardment in plasmas. The surface wettability in terms of water contact angle shows that the deposited Al2O3 layer can enhance the wetting property of modified PET surface. Further characterizations of the Al2O3 films suggest that the elevated density of hydroxyl -OH group improve the initial growth of ALD deposition. Chemical composition of the Al2O3-coated PET film was characterized by X-ray photoelectron spectroscopy, which shows that the content of C 1s reduces with the growing of O 1s in the Al2O3-coated PET films, and the introduction of plasma in the ALD process helps the normal growth of Al2O3 on PET in PA-ALD.

Surface Modification of Polyethylene Terephthalate (PET) by 172-nm Excimer Lamp

We studied the effects of 172 nm Xe2* excimer lamp irradiation on polyethylene terephthalate (PET) surfaces. Two kinds of techniques were applied: vacuum ultraviolet (VUV) light irradiation and VUV irradiation in the presence of oxygen gas (VUV/O3). The modified PET surfaces were investigated by using contact angle measurements which enabled the surface free energy to be calculated, X-ray photoelectron spectroscopy (XPS), nano-thermal analysis (nano-TA), and atomic force microscopy (AFM). The surface free energy increased significantly after the treatments. The results of XPS analysis showed that the elemental ratio of oxygen on the surface increased, whereas that of carbon decreased. From the deconvoluted C1s and O1s spectra, it was revealed that new oxidized functional groups such as alcoholic and carboxyl groups were generated. The nano-TA results showed that a low melting temperature (Tm) layer had formed on the VUV and VUV/O3 treated PET surfaces. The results of AFM measurements showed there were no remarkable changes after the treatments compared with untreated PET. In summary, the VUV and VUV/O3 treatments using a Xe2* excimer lamp not only change the surface functionalities but also reduce the Tm of the PET surfaces without significantly affecting the surface morphologies.

"Soft and rigid" dithiols and Au nanoparticles grafting on plasma-treated polyethyleneterephthalate

Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiols (1, 2-ethanedithiol (ED) or 4, 4'-biphenyldithiol) to create the thiol (-SH) groups on polymer surface. This "short" dithiols are expected to be fixed via one of -SH groups to radicals created by the plasma treatment on the PET surface. "Free" -SH groups are allowed to interact with Au nanoparticles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and electrokinetic analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the modified PET were studied by atomic force microscopy (AFM). The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on the modified surface only in the case of biphenyldithiol pretreatment. The possible explanation is that the "flexible" molecule of ethanedithiol is bounded to the activated PET surface with both -SH groups. On the contrary, the "rigid" molecule of biphenyldithiol is bounded via only one -SH group to the modified PET surface and the second one remains "free" for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface.

Quantification of Primary Amine Groups Available for Subsequent Biofunctionalization of Polymer Surfaces

Biocompatible polymers are commonly functionalized with specific moieties such as amino groups to modify their surface properties and/or to attach bioactive compounds. A reliable method is usually required to characterize amino group surface densities. In this study, aminated polyethylene terephthalate (PET) films were generated via an aminolysis reaction involving either ethylenediamine molecules (EtDA), in order to vary easily the amino group density on PET surfaces, or 25 kDa polyvinylamine (PVAm) as an alternative reagent preventing bulk damages resulting from the aminolysis reaction. Among commonly used dyes for amino group quantification, Orange II and Coomassie Brillant Blue (CBB) were selected to quantify the extent of amine grafting resulting from these derivatization procedures. Rapid and convenient colorimetric assays were compared to surface atomic compositions obtained from X-ray photoelectron spectroscopy (XPS) measurements. Orange II was found to be the most appropriate dye for quantifying primary amine groups in a reliable and specific way. Due to its unique negative charge and low steric hindrance compared to CBB, the Orange II dye was very sensitive and provided reliable quantification over a wide range of amino group surface densities (ca. 5 to at least 200 pmol/mm(2)). In order to further validate the use of the Orange II dye for amino group quantification, a heterobifunctional linker reacting with amino groups was then grafted on modified PET surfaces. Interestingly, the good correlation between the densities of adsorbed Orange II and covalently grafted linkers suggests that the Orange II method is a relevant, reliable, easy, and inexpensive method to predict the amount of amino groups available for subsequent functionalization of polymer surfaces.

Effects of operating parameters on DC glow discharge plasma induced PET film surface

A DC glow discharge plasma surface modification techniques are used to modify surface properties of polymeric materials such as adhesivity, hydrophobicity, hydrophilicity and biocompatibility. The plasma interaction with the surface produces modifications of its chemical structure and morphology. The objective of this study is to examine the effect of operating parameters such as discharge potential, pressure and exposure time on surface properties of polyethylene terephthalate (PET) film. The changes in hydrophilic properties of PET films were studied in detail using contact angle and surface energy measurements. The surface morphology and chemical composition of plasma modified film surfaces were studied by atomic force microscopy (AFM) and X-ray photo electron spectroscopy (XPS). It was found that the efficiency of the surface treatment increases with increasing discharge potential, pressure and exposure time. The AFM and XPS analysis showed changes in surface topography and formation of polar groups on the plasma modified PET surfaces.

Surface modification of polyethylene terephthalate with albumin and gelatin for improvement of anticoagulation and endothelialization

The surfaces of polyethylene terephthalate (PET) were modified by oxygen plasma-induced and ultraviolet (UV)-assisted acrylic acid (AAc) grafting polymerization, and the carboxyl ( COOH) groups on the PET surface was 5.29 × 10 −9mol/cm 2. Then using the COOH as reacting sites, the molecules of gelatin and bovine serum albumin (BSA) were further co-immobilized on the PET surface. The modified PET surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and surface chemical quantitative analysis. The results showed that the molecules of gelatin and albumin were immobilized on the PET surface. The concentration of gelatin on the gelatin-immobilized PET surface was 2.02 μg/cm 2. For the gelatin-immobilized PET surface, the human umbilical vein endothelial cells (HUVECs) culture attachment and proliferation ratios were improved, but the anticoagulation became worse proved by platelet adhesion test in vitro and the lactate dehydrogense (LDH) test. After further co-immobilization of albumin with gelatin biomolecules on the PET surface (PET-Gel–BSA), the percent of platelet adhesion in vitro decreased 28% than that on the gelatin-immobilized PET surface, and the cell density on the PET-Gel–BSA film (1.08 × 10 5 cells/cm 2) was significantly higher than that on the control PET surface. This investigation tries to find a method which can construct the anticoagulant surface before the endothelium formation and also accelerate the endothelialization of polymer surface.

Surface fluorination of polyethylene terephthalate films with RF plasma

The surface modification of polyethylene terephthalate (PET) by using low-pressure CF 4 plasma in a roll-to-roll double-sided treated system is investigated in this paper. The surface properties of the modified polymers are characterized by X-ray photoelectron spectroscopy (XPS) and water contact angle. Treated for a longer time and higher RF power (12 min, 600 W), the wettability of the PET surface shows two opposite extremes. The contact angle on one side of the PET film is super-hydrophilic, 7.56°, and the other side is hydrophobic, 108.63°. Furthermore, the modified PET surface dynamics is also considered and discussed after dipping the materials into different hydroxyl ion concentrations.

Investigations of the interface between magnesium and polyethyleneterephthalate by X-ray photoelectron spectroscopy

The interfacial chemistry between in-situ thermally evaporated magnesium and a polyethyleneterephthalate (PET) film is studied by X-ray photoelectron spectroscopy (XPS). The initially deposited Mg atoms adsorb on the PET surface, via an addition reaction to the CO groups, with the simultaneous formation of MgO and MgC bonds. Further metallization shows condensation in the agglomeration mode, with metallic clusters formed by adsorption on to the initial Mg at the PET interface. With exposure of the Mg/PET film to air, the interface does not change although the outer metallic component oxidizes. Rinsing this air-oxidized Mg/PET film with water removes all the magnesium and leaves a modified PET surface compared with its initial state.